Interactive Cat Toy Li-ion Battery BL-2600 Rechargeable Battery To Replace 3-pcs Size C Dry Batteries 3.7V Rechargeable lithium-ion Battery 2600mAh, Using the BL-2600 battery to Replacement 3-pcs size C dry batteries on these Cat's Meow Toy Compatible Interactive Cat toy V4 Version with Cat's meow toy V3,V2,V1. Rechargeable battery. Energy Saving,Environmentally friendly,Economy. Use USB wall charger or computer USB ports to charging. Red led light will show when charging and blue led light will show when full charged.